1. Field of the Disclosure
The present disclosure relates generally to frequency conversion of laser light from fiber lasers. More particularly, the disclosure relates to an apparatus for controlling lasing condition within a ring resonator provided with a piezoelectric mirror.
2. The Prior Art
A fiber laser provided with a second harmonic generation component and operative to provide the available frequency range, uniform output intensity, and high conversion efficiency is disclosed in U.S. Pat. No. 6,763,042 (“U.S. '042”), fully incorporated herein by reference. As shown in FIG. 1, a pump radiation 22 incident upon an input or pump mirror 34 of a ring resonator 14 leaks into the cavity. The leaked pumped radiation propagates along a light path within the cavity at a fundamental frequency and eventually impinges upon a piezoelectric mirror 36 having an actuator 40. The reflected pump radiation is further incident upon a first curved mirror 38 which reflects the pump light through a nonlinear crystal 30. Upon exiting the crystal, 90% of the leaked light are converted into an output light 32 which propagates through an output curved mirror 28 at a harmonic frequency and light at a resonant frequency remaining within the cavity. The light at the resonant frequency is reflected from mirror 34 and evaluated by a control circuitry 42. The control circuitry 42 is operative to evaluate the resonant frequency and compare it to a reference value. If the comparison is unsatisfactory, i.e. the resonant frequency is different from the fundamental frequency, a control signal is generated to shift piezoelectric mirror 36 so as to control a light path within the cavity until the resonant frequency and the frequency of the pump radiation are matched but are in antiphase.
The control circuitry disclosed in U.S. '042 is analog. The analog circuitry has a long reaction time and bulky. Furthermore, it is packaged with the rest of the laser system adding additional logistic problems.
Although a pump having a master oscillator power amplifier configuration operates in a continuous wave regime, many industrial applications including welding, cutting, tissue treatment and others require rather a quasi pulsed configuration. In other words, the output radiation should be interrupted. However, the control circuitry disclosed in the above-mentioned patent appears to not provide such a feature.
A need therefore exists for an improved fiber laser of the aforementioned type having a stand-alone controller.
A further need exists for a digitally operating controller.
Still a further need exists for controllably regulating the output of the fiber laser.